In the conventional injection molding of plasticized synthetic resin by an injection molder, the weight of the injected plasticized synthetic resin varies with the molten resin pressure, the molten resin specific volume or the molten resin temperature (including the influence of the disturbance on the molding system) etc.. Therefore, it is difficult to form products of a constant quality. To cope with this problem, so-called adaptive control a number of proposals have been made. The art disclosed in the Japanese Patent Laid Open Publication No. 84932 of Showa 56 (the year 1981) is an example.
Basically, in the adaptive control method, when the influence of a disturbance on the molding system and change in the molten resin pressure, molten resin temperature or mold temperature are detected, a controllable molding condition (pressure, time, etc.) other than the detected factors, are changed into a control factor, thereby assuring the constant product quality.
However, this control method has the following problems:
1 Preliminary study and analysis are necessary to determine the correlation between the detected factor according to the mold and the product quality and between the control factor and the product quality. PA0 2 With the same plasticized synthetic resin, the correlation between the detected factor and the product quality and between the control factor and the product quality varies greatly depending on the mold. Therefore, the study and analysis described in the item 1 above must be repeated each time the mold is changed. PA0 S.sub.H : the positional value of the screw during the dwelling process following the injection. PA0 A: projected sectional area of the screw PA0 V(P.sub.H): the molten resin specific volume value during the dwelling process following the injection PA0 V(P.sub.I): the molten resin specific volume value immediately before the injection. PA0 S.sub.H : the positional value of the screw during the dwelling process following the injection PA0 A: the projected sectional area of screw PA0 V(P.sub.H,T): the molten resin specific volume value for the molten resin temperature value T and the molten resin pressure value P.sub.H during the dwelling process following the injection at the molten resin temperature value T, and PA0 V(P.sub.I,T): the molten resin specific volume value for the molten resin temperature value T and the molten resin pressure P.sub.I immediately before the injection at the molten resin temperature value T.
In order to solve aforementioned problems, the present invention provides an injection control method of an injection molder, which assures the products of constant quality even when there is an influence to the molding system by the disorder from outside, there is a change in the given condition such as the change of the molten resin pressure and which does not require the analysis and the investigation from the beginning as in a case of the adaptive control method even the cavity is changed. the cavity is changed, and offers a molder products of of constant quality.